1. Field of the Invention
The present invention is related to a driving method and a related display device, and more particularly, to a driving method and a related display device capable of enhancing image brightness and reducing image distortion.
2. Description of the Prior Art
Liquid crystal displays (LCD), characterized in low radiation, small size and low power consumption, have gradually replaced traditional cathode ray tube (CRT) displays and been widely applied in various electronic devices, such as personal digital assistants (PDAs), flat-panel TVs or mobile phones. When used in portable electronic devices, battery duration is a major concern, but the backlight module of an LCD device consumes large amount of power. Therefore, many techniques capable of adjusting the brightness of the backlight module have been developed for power-saving purpose, commonly referred to as content adaptive backlight control (CABC) method. Although lowering the brightness of the backlight module can reduce power consumption, the overall brightness of the display images is also influenced. Therefore, the LCD device needs to enhance the brightness of the display images based on different image contents in order to maintain the image quality after performing the CABC technique.
In n-bit color depth display devices, each pixel has 2n gray levels, each of which corresponds to a specific voltage level. In other words, various degrees of bright/dark visual performances can be achieved by driving each pixel with 2n distinct voltage levels. Reference is made to FIG. 1 for a diagram illustrating the operation of a prior art n-bit color depth display device. Based on image signals, the prior art display device generates pixel data Dp_i for driving the backlight module, wherein i is an integer between 0 and n. Also, data slope is performed in which the pixel data Dp_i is multiplied by a predetermined rate Ki for generating corresponding pixel data Df_i. The pixel data Dp_i and Df_i can be related as follows:Df—i=Ki*Dp—i; where i represents gray level;    Ki is the predetermined rate corresponding to the ith gray level; and    Df_i is the pixel data of the ith gray level after performing data slope.
The relationship between the pixel data Dp_i and Df_i can be described by a partial-linear, non-linear or other specific transfer functions. However, all transfer functions aim at improving the brightness of the display images and only differ in the final effects. Since Ki is generally a floating-point value, the integer pixel data Dp_i are transformed into the floating-point pixel data Df_i after performing data slope. Since the digital-to-analog converter (DAC) of the display device only receives integer data, the floating-point pixel data Df_i have to be rounded off to the integer pixel data Do_i. Based on a predetermined gamma curve, the DAC converts the pixel data Do_i into analog voltages, thereby outputting the corresponding gamma voltage Vo_i for driving the display panel and the pixel data Dp_i for driving the backlight module.
Reference is made to FIG. 2 for a diagram illustrating the data slope operation in the prior art display device. In FIG. 2, the relationship between the pixel data Dp_i and Df_i can be described by a partial-linear transfer function, in which Ki equals to 1.2 for low gray levels and Ki equals to 0.65 for high gray levels. Since the DAC only receives integer data, the pixel data Do_i may lost a certain gray scale (such as when i=2 and i=3), causing unsmooth gray scale representation. Also, different pixel data Dp_i may be mapped to the same pixel data Do_i (such as when i=52 and i=53), causing loss in gray scale representation. Therefore, the display quality of the prior art display device is influenced due to image distortions.